As the price of gasoline continues to rise, the question often arises as to whether it makes financial sense to trade-in a 'gas guzzler' for a more fuel-efficient vehicle. Several factors will impact that decision, including the cost of the new vehicle, the number of miles you drive and the cost of fuel. You can calculate your monthly fuel savings based on your current miles per gallon, miles driven per month and cost of fuel. Then you can estimate how much you will save by purchasing a more fuel efficient vehicle and when you will breakeven on the fuel efficient vehicle purchase.